This application claims the benefit of Korean Patent Application No. 2000-1339, filed on Jan. 12, 2000, under 35 U.S.C. xc2xa7119, the entirety of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device. More particularly, it relates to an array substrate for use in a liquid crystal display device and a method of manufacturing the same.
2. Description of Related Art
A liquid crystal display (LCD) device includes a display and a pad. The pad applies electrical signals to the display, and thus includes drive circuitry. The display produces an image. The display itself includes upper and lower substrates, and an interposed liquid crystal layer.
FIG. 1 is a schematic perspective view illustrating a typical liquid crystal display (LCD) device 10. The LCD device 10 includes an upper substrate 11 and a lower substrate 17, which are opposed to and spaced apart from each other. A liquid crystal layer 19 is interposed between the upper substrate 11 and the lower substrate 17. A color filter 13 and a common electrode 15 are located under the upper substrate 11. A matrix array of switching devices 21 and pixels 23 are arranged on the lower substrate 17, which is often referred to as an array substrate. The resolution of the LCD device is dependent on the number of pixels 23. The size and number of the pixels 23 determine the size of the LCD device.
Each pixel 23 is defined by crossing gate lines 25 and date lines 27. Each pixel 23 includes a pixel electrode 29 that is made of a transparent conductive material. Electrical fields are produced across the liquid crystal layer 19 by voltages applied across the pixel electrodes 29 and the common electrode 15 (on the upper substrate 11). A thin film transistor (TFT) 21 is formed near the crossing of each gate line 25 and data line 27. Each TFT acts as a switching device that selectively applies a voltage to an associated pixel electrode 29. Each TFT 21 includes a gate electrode, a source electrode, and a drain electrode (none of which are shown in FIG. 1). Each gate electrode electrically connects to a gate line 25, and each source electrode electrically connects to a data line 27.
As previously indicated the resolution of the LCD device 10 depends on the number of pixels 23 on the array substrate.
FIG. 2 is a plan view illustrating a typical liquid crystal display (LCD) device 40, including pad drive circuitry. The LCD device 40 includes displaying elements and drive circuitry that controls the displayed image. The drive circuitry includes gate drive circuitry 41 and data drive circuitry 43. Referring to FIGS. 1 and 2 as required, the gate drive circuitry 41 is arranged along one end of the gate lines 25. The gate drive circuitry 41 applies electrical signals to the gate electrodes (not shown) via the gate lines 25. The data drive circuitry 43 is arranged at one end of the data lines 27, and the data drive circuitry 43 applies electrical signals to the pixel electrodes 29 via the data lines 27 and the TFTs 21. While not shown, the pad drive circuitry also includes a power supply and various other peripheral circuits.
The LCD device described above is typically used for small display devices, such as watches or electronic calculators. However, there is a trend to use LCD devices for large displays, such as computer monitors. To obtain a large-sized LCD device using conventional methods, either small-sized substrates are mated together, or a large-sized substrate must be fabricated.
FIGS. 3A and 3B are plan views illustrating various array substrates used to fabricate conventional large-sized LCD devices. FIG. 3A shows array substrates 55, each having a display portion 51, a data pad portion 53, and a gate pad portion 57. Electrical signals are applied to the display portion via the pad portions 53 and 57. In general, the gate pad portion 57 is arranged along either the left side or the right side of the display portion 51, while the data pad portion 53 is arranged along either the top edge or the bottom edge of the display portion 51.
In the conventional method of fabricating a large-sized LCD device, the small-sized array substrates are mated to form a large-sized array substrate. The mated array substrates are then joined to a large upper substrate. After that, the electrical drive circuitry is connected to the pad portions of the array substrate.
However, mating small-sized array substrates together requires a relatively complex mating process. FIG. 3B is a plan view illustrating a conventional large LCD device 61. During the fabrication of that large LCD device 61, electrical defects, such as open- and short-circuits, can occur during assembly. Typical defects include dot defects and line defects. For example, a dot defect is when a particular TFT does not operate when electrical signals are applied via the drive circuitry. An example of a line defect is when all of the TFTs connected to a gate line (or to a data line) do not operate due to a shorted or open gate line (or data line). Other types of defects are possible. For example, a particle might causes a simple cell defect in a 15xe2x80x3 display, but that same particle can cause a totally inoperative 30xe2x80x3 display.
In a small LCD device, the economic loss caused by a defect is relatively low because small LCDs are relatively inexpensive to manufacture. However, with large-sized LCD devices, the economic loss that results from a defect can be much larger, at least partially because the manufacturing costs of large-sized LCD devices are so much higher. Furthermore, the larger areas involved and the more difficult fabrication process cause large-sized LCD devices to generally have low manufacturing yields.
Accordingly, the present invention is directed to a liquid crystal display device that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the invention is to provide a method of fabricating an array substrate that can be used for large LCD device and for small LCD devices.
In accordance with the purpose of the invention, as embodied and broadly described, in one aspect the principles of the present invention provide a method of manufacturing a liquid crystal display device, including: forming (M+m) gate and (N+n) data lines to define (M+m)xc3x97(N+n) pixels on a substrate, including (Mxc3x97N) display pixels and (Mn+Nm+mn) redundant pixels; forming drive circuitry for operating each pixel; testing the (Mxc3x97N) display pixels for electrical defects (such as open- or short-circuits); and disabling the redundant pixels (leaving them in a dark state) when the display pixels do not have any defects.
The redundant pixels can be disabled by removing the drive circuitry for the redundant pixels, or by not forming that drive circuitry. Other ways of disabling the redundant pixels include controlling the drive circuitry such that the redundant pixels are not activated, by cutting gate and/or data lines to the redundant pixels, or by covering the redundant pixels, such as with a black matrix.
Beneficially, to form sufficient redundant pixels, n and m are great than 10. However, to avoid excess redundant pixels n and m are beneficially less than 20.
In accordance with another aspect of the principles of the present invention, there is provided a method of manufacturing a liquid crystal display device, including: forming a pixel matrix on an array substrate; testing the array substrate for electrical defects (such as open- or short-circuits); cutting the array substrate into a plurality of smaller array substrates if a defect is found such that a plurality of pixels along the cuts become redundant pixels; mating a smaller array substrate with an upper substrate; injecting a liquid crystal into a space between the smaller array substrate and the upper substrate; and sealing the space using a sealant. Beneficially, the sealant overlaps the redundant pixels. Also beneficially, an insulation material is formed along the cut edges of the smaller substrate.
In accordance with the purpose of the invention, in another aspect the principles of the present invention provide a method of manufacturing a liquid crystal display device, including: forming a pixel matrix on a first substrate; testing the pixels for electrical defects (such as open- or short-circuits); disabling some of the pixels (leaving them in a dark state) when defects are not found; mating a second substrate with the first substrate; injecting a liquid crystal into a space between the first and second substrates; and sealing the space with a sealant.